Hacettepe Üniversitesi Hastaneleri Merkez Laboratuvarından Ardışık Olarak İzole Edilen Acinetobacter Baumannii Klinik İzolatlarında Kolistine Direnç ve Heterodirencin Araştırılması
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Caglan, E., Investigation of Colistin Resistance and Heteroresistance of Acinetobacter baumannii Clinical Isolates Consecutively Isolated in Hacettepe University Hospitals Central Laboratory. Hacettepe University Institute of Health Sciences, MSc thesis in Microbiology, Ankara, 2017. A. baumannii has gained importance in recent years as it is common in the hospital environments and causes outbreaks, especially in intensive care units. Treatment options are very limited against this bacteria and in recent years colistin has been used as the most effective drug. However, colistin resistance and heteroresistance are being reported worldwide. In this study, our aim was to determine colistin resistance and heteroresistance rates in A. baumannii. isolated in our hospital. Susceptibility to colistin was determined by broth microdilution method in 200 isolates of A. baumannii isolated from various samples sent to hospital central laboratory. EUCAST standards were used throughout the study. Heteroresistance was investigated by Gradient (G-test) and PAP test. According to broth microdilution tests, 58 isolates (29 %) were resistant to colistin. Bacterial growth in the inner zone of the G-tests predicted heteroresistance and there were 3 isolates with this result. In addition, PAP analysis was employed on a total of 120 isolates including sensitive and resistant isolates. Mueller Hinton agars containing 0-10 mg / L of colistin were inoculated with 102 ve 103 cfu/mL of isolates and results were recorded. According to the PAP results, heteroresistance was not found in any isolates including the 3 isolates that suggested heteroresistance with the G-test. PAP test is the gold standard for determining heteroresistance in A.baumannii, and as it’s very labor intensive and time consuming, it cannot be performed easily in routine laboratories. This is the first study in Turkey investigating heteroresistance to colistin in A.baumannii with the PAP test. Resistance and heteroresistance to colistin in A.baumannii should be monitored periodically to guide the clinicians.